Page 1 PROGRESS REPORT THE SOLAR-A SOFT X-RAY TELESCOPE (SXT) PROGRAM (CONTRACT NAS8-37334) (for December 1994) OVERVIEW The YOHKOH Mission is a program of the Japanese Institute of Space and Astronautical Science (ISAS) with collaboration by the U. S. National Aeronautics and Space Administration and the U. K. Science and Engineering Research Council. The YOHKOH satellite was launched on 30 August 1991 from Kagoshima Space Center (KSC) in Japan. The purpose of this mission is to study high energy phenomena in solar flares and the sun's corona. Under an international cooperative agreement, Lockheed, under NASA contract, is providing a scientific investigation using the Soft X-ray Telescope (SXT), one of the primary experiments of the mission. The SXT was developed at the Lockheed Palo Alto Research Laboratory in cooperation with the National Astronomical Observatory of Japan, and the Institute for Astronomy of the University of Tokyo. MAJOR PROGRAMMATIC ACTIVITIES IN THE MONTH Although the Lockheed facility was closed for two weeks of the month, operations were continuous during that interval. Limited administrative activities were performed, but the RFP for FY 96 activities is still expected to be received later in this quarter. << Solar Activity >> Solar activity increased in December to a level more typical of this stage of the solar cycle. There was one major flare during the month. It came from NOAA Active Region 7815 on 14 December at about 05:30 U.T. and was classified as an M2 event by the GOES X-ray monitor. Most of the other flares recorded this month were from the same active region. The region appeared as a modest group of sunspots in white light, with the leading spot being positive polarity (i.e., outward-pointing magnetic field) and the trailing spots being negative polarity. The SXT observed the intense coronal emission associated with the large flare; however, close inspection of the soft X-ray images show that the magnetic field lines not only connect the leading and following spots but also stretch over several 100,000 km to the small "active region" ahead of AR7815 and a large area of surrounding plage. << Campaigns >> Page 2 We have been trying to observe the corona surrounding filaments and filament channels using SXT. This programme will continue in conjunction with various ground based H-alpha, magnetograph and radio telescopes. << Science >> Most of our effort in this holiday shortened month was devoted to a highly successful meeting of the American Geophysical Union held in San Francisco on 5-9 December. Yohkoh data was featured in the special session on results from Ulysses up to and including its polar passage earlier this year. We received expressions of interest and feedback on our various polar observations papers, particularly those involving our observations and interpretation of polar rays. << Publications>> The following list is an incomplete listing of work in progress on papers and presentations that include scientists that are supported by the NASA SXT contract. - Papers Published (1) - "A gigantic coronal jet ejected from a compact active region in a coronal hole," K. Shibata, N. Nitta, K.T. Strong, R. Matsumoto, T. Yokoyama, T. Hirayama, H. Hudson, and Y. Ogawara, Ap. J. (Lett.) 431, L51, 1994. - Papers accepted (5) - "Is the Solar Chromospheric Magnetic Field Force-Free?", T.R. Metcalf, L. Jiao, H. Uitenbroek, A.N. McClymont, and R.C. Canfield, Astrophys. J., to be published 1995. "The large-scale coronal eruptive event of April 14, 1994", D. Alexander, G.L. Slater, H.S. Hudson, A.H. McAllister, and K.L. Harvey, Proc. 3rd SOHO Workshop, to be published 1995. "Resolving the 180 Degree Ambiguity in Vector Magnetic Field Measurements: The 'Minimum' Energy Solution", T. R. Metcalf, Solar Phys. to be published, 1995. "Comment on 'The Solar Flare Myth'", H.S. Hudson, B.M. Haisch, and K.T. Strong, J.G.R. to be published, 1995. "Coherent brightness variations in solar radiative output from the photosphere to the corona", J.L. Lean, J.T. Mariska, K.T. Strong, H.S. Hudson, L.W. Acton, G.J. Rottman, T.N. Woods, and R.C. Willson, G.R.L., to be Page 3 published 1995. "Energetic Particles in Solar Flares", H.S. Hudson and J.R. Ryan, Ann. Revs. Astron. Astrophys., to be published 1995. - Presentations (10) - "Combined Soft X-ray and Hard X-ray Spectra for Solar Flares Derived from Yohkoh Observations" by McTiernan, Fall AGU, December 1994, San Francisco. "Coronal Bright Points and High Speed/High Latitude Solar Wind Streams", by S. Suess, G. Poletto, M. Neugebauer, B. Goldstien, J. Khan, Y. Uchida, E. Hiei, K. Strong, and K. Harvey, Fall AGU, December 1994, San Francisco. "Yohkoh SXT Observations of Solar Polar Coronal Holes" by G. Linford, G. Slater, J. Lemen, and K. Strong, Fall AGU, December 1994, San Francisco. "Yohkoh Observations of Polar Rays" by K. Strong, R. Fisher, and M. Guhuthakurta, Fall AGU, December 1994, San Francisco. "Observations of Polar X-ray Bright Points by Yohkoh SXT", by N. Nitta, K. Strong, J. Lemen, and K. Harvey, Fall AGU, December 1994, San Francisco. "Spatial and Temporal Correlations between Polar Arcade Eruptions and the Variability of the Polar Coronal Hole Boundaries", by G. Slater, Fall AGU, December 1994, San Francisco. "Yohkoh SXT Observations of the Polar Region", by J. Lemen, Fall AGU, December 1994, San Francisco. "NO Concentration in the lower Thermosphere: Analysis of ATMOS observations using Yohkoh SXT Data", by P. Swaminathan, C. Kumar, L. Acton, M. Gunson, Fall AGU, December 1994, San Francisco. "Observations of the Annular Solar Eclipse of 10 May 1994" by P. Hick, B. Jackson, R. Altrock, K. Strong, G. Slater, and T. Henry, Fall AGU, December 1994, San Francisco. "Current-Carrying Magnetic Flux Emergence in AR 7260", ISAS seminar, K. D. Leka, December 1994. << Public Use of SXT Images >> We have had an influx of requests for videos and Page 4 posters as a result of presentations given at the AGU. We handed out nearly 300 posters to other scientists, teachers, students, and members of the press corps at the meeting itself. A set of SXT images have been supplied to NSF to be put up in the lobby of their headquarters building near Washington. G. Linford and K. Strong wrote another in their series of Sky & Telescope articles on solar activity as seen by Yohkoh. G. Linford also gave an introductory astronomy presentation to kindergartners and first graders at Cherry Chase Elementary School in Sunnyvale CA. This presentation covered the solar system with a focus on the Sun and planets. It was interesting to explain to the children why a 14" model of the moon has a smooth and featureless back side. This was the first to two 1 hour presentations on introductory astronomy. The second presentation will be done next week and will focus on the concept of day and night, and gravity. << Yohkoh Operations and Health >> Yohkoh and the SXT continue to function well. No significant degradation in the instrument has occurred since the loss of the front thermal shield in 1992. The SXT experienced a number of false flare flags during December on entry to the SAA. This problem was fixed by a minor modification to the operation software. SXT experienced a normal level of SEU events during the month: Datrg error Pass 2 6 December 1994 Bitmap error Pass 1 12 Decmeber 1994 Bitmap error Pass 1 23 December 1994 Bitmap error Pass 2 23 December 1994 We also set up the plan for the long New Year break (29 December 1994 - 3 January 1995) Page 5 << Data Flow >> ------------------------------------------------------------------------------ Month Full Frame Images Observing Region Images Received Lost Received Lost Loss % QT FL Tot Thru Sep-92 72097 35391 237694 133568 371262 134950 26.30 Oct-92 6753 2552 51037 14709 65746 23529 26.36 Nov-92 6648 2949 24345 14832 39177 12859 24.71 Dec-92 6766 3008 24188 6600 30788 12454 28.80 Jan-93 6888 3351 24067 4861 28928 13069 31.12 Feb-93 6833 3004 24479 18149 42628 12302 22.40 Mar-93 7177 3460 25874 19537 45411 14657 24.40 Apr-93 7754 3644 34128 8352 42480 17967 29.72 May-93 8571 3950 41832 7518 49350 21971 30.81 Jun-93 7340 2589 64545 12539 77084 26299 25.44 Jul-93 8259 3650 47561 5352 52913 24213 31.39 Aug-93 7628 3638 30705 3563 34268 17436 33.72 Sep-93 6875 2899 22697 5600 28297 11252 28.45 Oct-93 7474 3657 33782 7548 41330 20104 32.72 Nov-93 8504 3864 42953 5849 48802 23896 32.87 Dec-93 5898 3047 21128 13297 34425 13001 27.41 Jan-94 6934 2804 28567 10960 39527 13746 25.80 Feb-94 7000 2840 23021 5819 28840 11257 28.07 Mar-94 7736 2627 69273 3733 73006 31464 30.12 Apr-94 6142 2741 22707 3390 26097 12338 32.10 May-94 7070 2679 25260 3040 28300 10862 27.74 Jun-94 7417 2738 36795 1996 38791 15760 28.89 Jul-94 7488 2941 50540 3275 53815 24153 30.98 Aug-94 7370 2337 35067 3993 39060 13485 25.66 Sep-94 7079 2552 25131 2855 27986 10677 27.62 Oct-94 7244 2497 25868 5884 31752 10319 24.53 Nov-94 6569 1941 26243 1956 28199 9293 24.79 Dec-94 3611 1359 16344 1902 18246 7331 28.66 Total 263125 114709 1135831 330677 1466508 570644 28.01 Number of Full Frame Images Received: 263125 Number of Observing Region Images Received: 1466508 Total: 1729633 Approximate Number of Shutter Moves/CCD Readouts: 3009497 NOTES: * The loss of images is mainly due to BDR overwrites, but there are also occasional DSN dumps which are lost. * It is common to have observing regions which contain more than 64 lines, which requires multiple exposures to make a single observing region image. This is why the number of shutter moves is larger than the number of images received plus those lost. Page 6 << Engineering Summary Table >> -------------------------------------------------------------------------------- Month Avg Dark Level # of Dark Spikes CCD Warmings Front Optical (DN) (e/sec) Over 48 Over 64 High / # Support Trans Temp /Days Temp (%) Oct-92 32.64 80.3 2317 1055 16.8 11.5 Nov-92 36.24 215.1 6112 1391 18.0 11.0 Dec-92 42.58 452.8 17390 2024 17.9 N/A Jan-93 42.59 453.1 13006 2034 23.8 / 2 19.2 N/A Feb-93 42.28 441.5 13895 2090 17.7 N/A Mar-93 43.14 473.8 14047 2151 17.7 N/A Apr-93 43.13 473.4 14304 2146 23.8 / 2 16.9 N/A May-93 43.45 485.3 16405 2357 17.3 N/A Jun-93 44.03 507.2 20037 2531 16.3 N/A Jul-93 44.52 525.6 23977 2700 22.5 / 2 17.7 N/A Aug-93 44.24 515.0 21879 2643 25.2 / 3 17.2 N/A Sep-93 45.07 546.2 27469 2745 17.5 N/A Oct-93 45.40 558.6 31684 2982 17.7 N/A Nov-93 45.33 555.8 32047 3210 23.8 / 3 19.7 N/A Dec-93 45.92 578.1 38515 3101 19.2 N/A Jan-94 46.18 587.9 42560 3464 22.5 / 2 20.3 N/A Feb-94 46.03 582.1 40449 3246 19.3 N/A Mar-94 45.92 578.0 39715 3420 18.2 N/A Apr-94 45.97 579.9 41302 3721 25.2 / 3 17.8 N/A May-94 46.25 590.3 45476 3557 18.3 N/A Jun-94 45.83 574.6 39340 3547 17.8 N/A Jul-94 46.76 609.5 53417 3990 18.2 N/A Aug-94 47.02 619.0 58434 4121 25.2 / 3 18.2 N/A Sep-94 47.07 620.9 58580 4028 18.3 N/A Oct-94 47.34 631.3 64974 4346 19.0 N/A Nov-94 47.64 642.4 70877 4703 20.4 N/A Dec-94 47.77 647.2 73557 4865 19.8 N/A NOTES: * The dark current calculations are using full half resolution 2.668 sec images not taken in during the SAA. The dark current rate assumes a "fat zero" of 30.5 DN and a gain of 100 e/DN. * The entrance filter failure of 13-Nov-92 eliminated the capability of taking optical images, so the optical transmission is not available after Nov-92. It also caused an increase in the dark current signal, however some of the increase shown here is an increase in the readout noise and is not a function of exposure duration. Page 7 << Personnel Travel >> SXT Foreign Travel between 1-DEC-94 and 31-DEC-94 ACTON 1-DEC-94 * 22-DEC-94 22 (total of 22 days) FREELAND 1-DEC-94 * 22-DEC-94 22 (total of 22 days) HUDSON 1-DEC-94 * 22-DEC-94 22 31-DEC-94 31-DEC-94 * 1 (total of 23 days) NITTA 19-DEC-94 31-DEC-94 * 13 (total of 13 days) LEKA 1-DEC-94 * 2-DEC-94 2 (total of 2 days) ---------------------------------------------------------------- Grand Total of 82 days for 5 people NOTE: The "*" signifies travel that actually ends after 31-DEC-94 SXT Foreign Travel between 1-JAN-95 and 31-JAN-95 HUDSON 1-JAN-95 * 8-JAN-95 8 15-JAN-95 31-JAN-95 * 17 (total of 25 days) LEMEN 4-JAN-95 31-JAN-95 * 28 (total of 28 days) NITTA 1-JAN-95 * 17-JAN-95 17 (total of 17 days) SLATER 5-JAN-95 31-JAN-95 * 27 (total of 27 days) CANFIELD 16-JAN-95 31-JAN-95 * 16 (total of 16 days) ---------------------------------------------------------------- Grand Total of 113 days for 5 people NOTE: The "*" signifies travel that actually ends after 31-JAN-95 Respectfully submitted, Keith T. Strong Frank Friedlaender Page 8 =================================================== MSU Activity Report for November and December 1994 =================================================== Loren Acton spent November working on a a study of the Yohkoh cusp events with Terry Forbes and Saku Tsuneta. These events are suggestive of reconnection and the detailed analysis of the Yohkoh data with the strong theoretical input of Terry Forbes should yield some interesting results. Loren also laid the ground for the 1996 SEIIM/Chapman Conference to be held here at MSU. (SEIIM stands for Solar Events and their Influence on the Interplanetary Medium). Some effort went into reassessing the MSU/TRACE budget. Loren also worked some with Adina Ragenovich and Sergey Katsov (see below). In December, Loren was at ISAS as SXT Chief Observer where he concentrated on calibration issues. Loren's work will markedly improve the data anlysis of the Yohkoh team. David Alexander spent the first part of November at ISAS as Chief Observer. The main activity involved planning and observing the solar eclipse of Nov 3. This proved to be successful and together with Husdon, Hara and Kano a team bulletin board item was written proposing to analyse the occultation data with the hope of obtaining sub-pixel resolution of a solar soft X-ray loop structure. A paragraph describing the Yohkoh eclipse observations, together with some images was sent to Jay Pasachoff. David discussed the analysis of SXV data with Louise Hara and Bob Bentley for use in the NATO funded coronal heating project with the assistance of Jim Lemen and Sam Freeland. He also worked with Sergey Katsov on an SXT loop geometry project, see below. David participated in the NASA Solar MOWG meeting in Greenbelt, Maryland in the early part of December. Finally, he has spent a lot of time in preparing to teach a graduate course in astrophysics. Brian Handy switched to the TRACE project at Lockheed and spent much of November and December travelling between Bozeman and Palo Alto. During this time he trained Mark Weber in the intricacies of system management of the MSU solar group computers as well as carrying out his system operations duties which included updating our IDL to version 3.6.1. Mark Weber embedded himself in the computers for much of the period reported here. He worked closely with Brian Handy on learning the system duties and also followed on from Brian's work in setting up the video and movie making facilities here at MSU. Mark worked with Sergey on loading the SFD data from tape onto disk in preparation for his research work on the rotation of the solar corona. Adina Ragenovich continued working with Loren Acton and David Alexander on her "particle systems" approach to visualizing loop filling. Adina is looking at how the particles behave in a varying magnetic field when collisions are involved. Sergey Katsov was employed as an undergraduate work study to help Mark with the manual labour of laoding data from tape to disk. Sergey has also been working with David on the study of geometrical effects on the interpretation of SXT data. Page 9 UCB YOHKOH/SXT PROGRESS REPORT (5-JAN-1995) J. McTiernan presented a paper titled "Combined Soft X-ray and Hard X-ray Spectra for Solar Flares Derived from Yohkoh Observations" at the Fall AGU Meeting, held in San Fransisco from 5 December to 9 December, 1994. This presented results for the impulsive footpoint and gradual looptop sources in the flare of 2-Nov-91. Similar work has now been done for the flares of 13-Jan-92, 6-Feb-92, and 17-Feb-92. (This work has been presented at seminars here at UCB, and at Stanford, but is is not ready for publication.) The major motivation for this work was the testing of methods for the calculation of expected uncertainties in HXT images. It was found that the nonthermal electron spectra calculated from HXT footpoint spectra can account for the gradual Soft X-rays observed by SXT via chromospheric evaporation if the electron low energy cutoff is as low as 20 keV for small flares (e.g. 13-Jan-92 and 17-Feb-92) and for a cutoff energy of 30 keV for the large flare of 2-Nov-91. The large uncertainties in the spectra derived from HXT images (10% in spectral index) make this a very tentative conclusion. We are also working on the uncertainty in SXT plasma measurements due to photon statistics, scattering, compression, interpolation, etc... McTiernan hopes to have a first draft of a paper on this subject complete after a visit to ISAS from 10-Feb-95 to 25-Feb-95. Page 10 UNIVERSITY OF HAWAII ACTIVITY REPORT (R. CANFIELD) MAJOR ACTIVITIES FOR THE MONTHS OF NOVEMBER AND DECEMBER Our most important activities included support of Yohkoh operations and data analysis at ISAS, coordinated ground-based data acquisition at Mees, analysis of Yohkoh/Mees data, preparation of manuscripts, and completion of K. D. Leka's thesis, which was based on data from Yohkoh and the Imaging Vector Magnetograph (IVM) at Mees. Operational support for SXT and designated campaigns was provided by Hudson and Leka at ISAS, by Judd, Nitta, and Douglass at Mees, and by Canfield, Jiao, Metcalf, and Wuelser in Manoa. Jiao continued to digest the techniques used in Mikic's resistive mhd code for the computation of theoretical 3-D force-free coronal magnetic fields and studied related textbooks and materials. He is still in the process of developing and documenting procedures that carry out all the jobs associated with application of Mikic's code to Mees Stokes magnetograms and comparison of the results with Yohkoh SXT data. For the latter purpose, he studied various standard display programs. Leka defended her dissertation on 1 November, then travelled to ISAS for a one-month stay. She performed Yohkoh Tohban duty for one week, and also worked on some coalignment questions. She formatted her dissertation to meet U. Hawaii requirements, and the document will be distributed to requesting team members once it has been duplicated. She has now moved to a postdoctoral position at HAO/NCAR, working on magnetic fields in sunspots and sunspot evolution. She will continue to collaborate with Yohkoh collegues in Japan and Hawaii, and thanks the Yohkoh team for a productive graduate career! Reardon worked with Hudson in planning Yohkoh observations of the November 3rd total solar eclipse and helped to coordinate observations by the ground-based teams at Putre with the SXT observations. Most experiments at Putre with limited field-of-views made an effort to concentrate on the east limb, where the moon's path over the Sun (as seen from the spacecraft) gave Yohkoh the best data. In addition, Yohkoh full-disk soft X-ray images from previous rotations and in the days leading up to the eclipse, received on site via fax, were used by all the teams to help predict the appearance of the corona during totality Page 11 and plan their observations.Metcalf installed an improved version of the pixon code to reconstruct images from the Yohkoh Hard X-ray Telescope. He continued his study of ion acceleration in flares through the analysis of Mees Imaging Vector Magnetograph (IVM) observations of H-alpha polarization during flares observed by Yohkoh and began writing a paper on the results. He began a study of the affect of spatial resolution and filling factor on the resolution of the 180 degree ambiguity in vector magnetograms, to aid in analyses of IVM observations coordinated with SXT data. Finally, he digitized several Mees H-alpha coronagraph images for the November solar eclipse. Wuelser started putting together the results of his study of chromospheric evaporation and energetics in large flares. He previously presented first results at the Solar Physics Division meeting in Baltimore, and now needs to fill in some gaps in the analysis before writing up the work. He also continued to collaborate with Bastian on the well-observed Yohkoh/VLA/Mees flare of August 20, 1992. The focus of the current work is to understand the relationship between the microwave emission and the magnetic field strength and filling factor in the various flare sources. Finally, Wuelser made the Mees full disk white light images available to the public. Daily images are kept for 30 days in an on-line archive, and can be retrieved by anonymous ftp. Hudson worked on several data analysis projects. The most interesting of these is a study of over-the-limb flares seen by BCS and SXT: with a set of four similar flares within one day, all from the same active region, we have been able to isolate the loop-top signal in BCS. This is of course one of the most puzzling discoveries within the Yohkoh observations, in that we observe unexpectedly bright compact regions at the apparent tops of compact flare loops. With the present analysis we hope to learn something about the physical conditions in these interesting sources. A second Hudson project involves flares and CMEs. Analysis of the celebrated cusp event of 21 February 1992 had shown that a large volume of coronal material "disappeared" just prior to the flare, and during the ejection of a blob-like mass from near the cusp itself. The "disappearing corona" suggests the launching of a CME, whose mass originates in hot coronal material. This behavior has now been confirmed with a particularly well-observed event of 13 November 1994, which was not quite bright enough for flare mode to trigger, and for which Yohkoh accordingly got full-Sun data showing the entire corona. In this event the coronal Page 12 disappearance is unambiguous and yields a lower limit on mass of 4x10^14 g. The timing is different, in that the coronal disappearance occurs after the rise phase of the soft X-ray event, rather than before. The 13 November ejective event has been written up in a draft manuscript with Acton and Freeland. This paper describes more than the "disappearing corona", since this flare also had a remarkable sequence of ejections from the site of the post-flare loop development. These ejections occur in the form of fine loops without any suggestion of the jet or shock structures expected from the standard model. On the other hand, another gradual event from the same active center (19 October 1994) showed a quite different development that suggested filament eruption. Finally, with the help of Acton and many people involved in the special problems of SXT data at extremely low light levels, Hudson re-reduced the data from the eclipse of November 3. The new reduction is much cleaner for the whole-Sun images, in spite of the dramatic temporal modulation of the stray light level caused by the eclipse itself.Cauzzi worked with Van Driel-Gesztelyi, Schmieder, Nitta, Kurowawa and others on the analysis of X-ray bright point observations that were part of a Yohkoh campaign organized by Schmieder in April - May 1993. Strong magnetic flux emergence took place during this campaign; the Mees Stokes polarimeter played an important role, by providing evidence for the overall active-region magnetic evolution and specifics of magnetic flux emergence on the day of greatest interest. The location of X-ray emission appears at the separator between emerging and old flux for an extended period of time. Canfield worked with Reardon on their paper with Leka, Shibata, Yokoyama, and Shimojo on surges and jets in AR 7260. He also worked with Leka on her thesis and the associated paper on evidence that magnetic flux in AR7260 carried currents prior to its emergence at photospheric levels. Finally, he worked with Li, Metcalf, and Wuelser on the spatial relationship between flare hard X-ray emission (from HXT data) and active-region electric currents (from Mees Stokes magnetograms). Finally, Canfield and Reardon worked with Shibata and Martin on simultaneously observed Mees H-alpha and Yohkoh soft X-ray eruptive prominence events. PLANS FOR JANUARY AND FEBRUARY During the Spring semester Jiao will temporarily reduce his level of effort on the Yohkoh project, in order to work half time as a teaching assistant. However, he will continue to work part time on his thesis and serve as Mees Page 13 Duty Scientist during this period. Metcalf plans to continue the analysis of the IVM H-alpha polarization data in conjunction with the Nobeyama data, complete the 180 degree ambiguity study, and start work on a new version of the SXT pixon code. Wuelser plans to write up his chromospheric evaporation and energetics study. He will continue his collaborations with Bastian on the August 20, 1992 flare, and with Rolli on two flares that were well observed by Yohkoh and the dual high speed optical imaging spectrograph of the University of Bern. Hudson will prepare a paper on homologous limb events, co-authored with Khan, Harra, Lemen, and Sterling. The paper on the 13 November ejective event, written with Acton and Freeland, will be polished and submitted to Ap. J. Other work in progress during these two months may include assistance to J.-P. Wuelser on the analysis of the Mercury transit data, and assistance to F. Farnik and T. Watanabe in analysis of hard-spectrum events and soft X-ray precursors. Canfield will spend January 17 - February 10 in Japan, where he will collaborate with Shibata, Yokoyama, and Shimojo to complete the paper on H-alpha surges and X-ray jets in AR 7260 and serve as SSOC toban. He will continue to collaborate with Li, Metcalf, and Wuelser on the spatial relationship between HXT footpoint emission and active region currents inferred from vector magnetograms.Cauzzi expects to finish the X-ray bright point work with Van DrielGesztelyi et al and submit it for publication. Page 14 Yohkoh/SXT Activity Report Stanford Team November/December 1994 During the last two months, Sturrock has continued his research into ejection mechanisms relevant to both cool ejections such as surges, and high-temperature ejections such as those observed by means of SXT. Although it is tempting to search for a common mechanism, the parameters of the two processes are so different that it seems more likely that two different processes are involved. The ejection process of a surge probably involves the driving of cool gas by magnetic stresses, either on a continuous basis if the motion is non-ballistic, or impulsively if the motion is predominantly ballistic. It seems that there is still no consensus concerning whether or not the motion of gas in surges is or is not ballistic. On the other hand, the ejection process of an X-ray jet is most likely hydrodynamic, although it is likely that magnetic-field reconnection is initially involved in heating the gas to X-ray temperatures. Sturrock has also continued to collaborate with Loren Acton in analyzing SXT information concerning coronal heating. It appears that one must distinguish the active-region corona, mainly composed of coronal loops with a wide range of size, shape and brightness, from the diffuse corona that extends well above active regions. Coronal loops must be heated by a mechanism that confines energy release to a small region - or at least to a localized flux tube. Flare-like heating, due to energy release in a localized reconnection event, seems most promising for this purpose. On the other hand, heating of the diffuse corona requires energy input that is extended rather than confined. Wave heating is most promising for this purpose. However, waves responsible for heating the diffuse corona may not originate near the surface of the Sun, but may instead originate in the chromosphere or corona, either from impulsive MHD events (such as the events responsible for spicules), or from frequent, small, reconnection events occuring at coronal heights. Klimchuk returned to the study of pressure/length and temperature/length correlations in coronal loops. The paper describing this work has been significantly revised, and it should be ready for submission to the Astrophysical Journal in the very near future.Roumeliotis has continued to apply the maximum likelihood image reconstruction method to interesting-looking flares, many of which turn out to resemble the classical picture of loops interacting at an x-type reconnection site. Page 15 Roumeliotis has also been making theoretical calculations on a specific model of MHD wave absorption in the corona. In the presence of a magnetic null point (where the field strength vanishes), MHD waves launched from below are very efficiently absorbed in the vicinity of the null point. The sharp corners seen in many X-ray images are likely to be signatures of magnetic null points, so the proposed wave absorption mechanism may be helpful in understanding the heating of these intriguing structures. Page 16 Solar Physics Research Corporation Activity Report Karen L. Harvey Activity the last two months are as follows: (1) An XBP campaign was requested and is scheduled for January 9-16 1995. This campaign, weather and solar activity permitting, is to continue the study of the variations and association of He I 10830 dark points to X-ray bright points. The previous attempts at obtaining simultaneous SXT and He I 10830 observations were marginally successful in acquiring sufficient observations to accomplish this goal. (2) Continuing the reduction of observations obtained in collaboration by Yohkoh SXT, NSO/KP, BBSO, and MSO during several of the XBP campaigns. This includes the registration and cleaning up of the SXT PFIs and registration and co-alignment of the simultaneous NSO/KP magnetograms and He I 10830 spectroheliograms of the target areas with the SXT data. (3) Continuing work on the analysis of the 14 April 1994 arcade event with David Alexander, Hugh Hudson, and Alan McAllister. Two viewgraphs of a comparison of the NSO/KP He I 10830 spectroheliogram and of the SXT FFIs on 13 April and on 14 April 1994 were prepared and submitted to W. Wagner at NASA. (4) Preparation of NSO/KP magnetograms and He I 10830 spectroheliograms for several investigators involved in analysis of SXT data. (5) Continuing the collection and updating of the bibliography of Yohkoh papers. Page 17 ------------------------------------------------------------------------------- NASA REPORT DOCUMENTATION PAGE (IN LIEU OF NASA FORM 1626) --------------------|--------------------------|------------------------------- 1. REPORT NO. | 2. GOVERNMENT | 3. RECIPIENT'S DR-01 | ACCESSION NO. | CATALOG NO. --------------------|--------------------------|------------------------------- 4. TITLE AND SUBTITLE | 5. REPORT DATE Monthly progress report - for the month of | 10 January 1995 December 1994 |------------------------------- | 6. PERFORMING ORG | CODE: O/91-30 -----------------------------------------------|------------------------------- 7. AUTHOR(S) | 8. PERFORMING ORGANIZA- K. T. Strong | TION REPORT NO: F. M. Friedlaender | |------------------------------- -----------------------------------------------|10. WORK UNIT NO. 9. PERFORMING ORGANIZATION NAME AND ADDRESS | Lockheed Palo Alto Research Labs B/252 |------------------------------- Solar & Astrophysics Laboratory O/91-30 |11. CONTRACT OR GRANT NO. 3251 Hanover Street, Palo Alto Ca. 94304 | NAS8 - 37334 -----------------------------------------------|------------------------------- 12. SPONSORING AGENCY NAME AND ADDRESS |13. TYPE OF REPORT AND Marshall Space Flight Center (Explorer Program)| PERIOD COVERED Huntsville Alabama 35812 | Progress report for the month | of December 1994 |------------------------------- |14. SPONSORING AGENCY | CODE MSFC / AP32 -----------------------------------------------|------------------------------- 15. SUPPLEMENTARY NOTES ------------------------------------------------------------------------------- 16. ABSTRACT The SOLAR-A Mission is a program of the Institute of Space and Astronautical Science (ISAS), the Japanese agency for scientific space activity. The SOLAR-A satellite was launched on August 30, 1991, to study high energy phenomena in solar flares. As an international cooperative agreement, Lockheed, under NASA contract, is providing a scientific investigation and has prepared the Soft X-ray Telescope (SXT), one of the two primary experiments of the mission. --------------------------------------|---------------------------------------- 17. KEY WORDS (SUGGESTED BY | 18. DISTRIBUTION STATEMENT AUTHOR(S)) Solar-A, X-ray, CCD, | Space Science, Solar Physics ------------------------|-------------|----------|-----------------|----------- 19. SECURITY CLASSIF. | 20. SECURITY CLASSIF. | 21. NO OF PAGES |22. PRICE (OF THIS REPORT) | (OF THIS PAGE) | | None | None | 17 | ------------------------|------------------------|-----------------|----------- For sale by: Superintendent of Documents, U.S. Government Printing Office